1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of manufacturing the same. More particularly, the invention relates to a liquid crystal display device which includes a liquid crystal panel having a pair of substrates facing each other, a liquid crystal layer disposed between sides, of the pair of substrates, facing each other, and a pair of electrodes formed on a surface side, of one substrate, facing the other substrate, a transverse electric field being applied to the liquid crystal layer through the pair of electrodes, thereby displaying an image in a pixel area, in which a light receiving element is formed on a surface, of the one substrate, facing the other substrate, and a method of manufacturing the same. In this case, the light receiving element receives an incident light made incident from the side of the other substrate to the side of the one substrate through the liquid crystal layer on a light receiving surface thereof, thereby generating data on the received light.
2. Description of the Related Art
A liquid crystal display device includes a liquid crystal panel having a liquid crystal layer enclosed between a pair of substrates as a display panel. The liquid crystal panel, for example, is of a transmission type, and modulates and transmits a radiation light emitted from a radiation device such as a backlight provided on a back surface thereof. Also, an image is displayed on a front surface of the liquid crystal panel based on the radiation light thus modulated.
The liquid crystal panel, for example, utilizes an active matrix system. Thus, the liquid crystal panel includes a TFT (Thin Film Transistor) array substrate, a counter substrate, and a liquid crystal layer. In this case, a plurality of TFTs each serving as a pixel switching element are formed in a pixel area of the TFT array substrate. The counter substrate is disposed so as to face the TFT array substrate. Also, the liquid crystal layer is disposed between the TFT array substrate and the counter substrate.
In the liquid crystal panel utilizing the active matrix system, a potential is applied to a pixel electrode through the pixel switching element to apply an electric field generated across the pixel electrode and a common electrode, thereby changing an orientation of liquid crystal molecules of the liquid crystal layer. As a result, a transmittance of each of lights transmitted through the pixels, respectively, is controlled, and the lights thus transmitted are modulated, thereby displaying an image.
In such a liquid crystal panel, there are known various display modes such as a Twisted Nematic (TN) mode, an Electrically Controlled Birefringence (ECB) mode, and a vertical orientation mode. In addition thereto, a Fringe Field switching (FFS) system, or an In-Plane-Switching (IPS) system, and the like are known as modes with each of which a transverse electric field is applied to the liquid crystal layer. In each mode with which the transverse electric field is applied to the liquid crystal layer, there is no dielectric anisotropy of the liquid crystal modules when viewed in a direction of the gaze, and thus it is possible to realize the suitable wide viewing angle. This technique, for example, is described in Japanese Patent Laid-Open No. 2007-226200.
A liquid crystal display device is proposed in which in the liquid crystal panel as described above, in addition to a semiconductor element such as a TFT serving as a pixel switching element, a light receiving element for receiving a light to obtain data on the received light is built in a pixel area. For example, PIN (P-intrinsic-N) type photodiodes are integrated as the light receiving elements in the pixel area. This technique, for example, is described in Japanese Patent Laid-Open Nos. 2006-3857 and 2007-128497.
In the liquid crystal panel described above, the light receiving elements built therein are utilized as position sensing elements, thereby making it possible to realize a function as a user interface. In the liquid crystal panel of this type, it is unnecessary to specially provide an external touch panel utilizing a resistor film system or an electrostatic capacitance system on the front surface of the liquid crystal panel. Therefore, it is possible to reduce a cost of the liquid crystal display device, and it is possible to readily realize miniaturization and thinning of the liquid crystal display device. Moreover, when the touch panel utilizing the resistor film system or the electrostatic capacitance system is installed, the quality of the displayed image may be reduced because the touch panel may reduce a quantity of light transmitted through the pixel area or may interfere with the light concerned. However, this problem can be prevented from being caused by building the light receiving elements as the position sensing elements in the liquid crystal panel in the manner as described above.
In the liquid crystal panel, for example, the radiation lights emitted from the backlight are transmitted through the liquid crystal panel, so that the light receiving element built in the liquid crystal panel receives a visible light obtained by reflecting the radiation lights from an object to be detected such as the finger of a user or a stylus pen which touches the front surface of the liquid crystal panel. After that, a coordinate position where the object to be detected touches the front surface of the liquid crystal panel is identified based on the data on the received light obtained from the light receiving element. Also, a manipulation corresponding to the coordinate position thus identified is carried out in the liquid crystal display device itself or in an electronic apparatus including the liquid crystal display device.
When the coordinate position of the object to be detected is detected by using the light receiving element built in the liquid crystal panel in the manner as described above, the data on the received light obtained from the light receiving element contains therein many noises due to an influence of the visible light contained in an outside light in some cases. In addition, when a dark image is displayed as in the case of black display, it is difficult for the light receiving element to receive the visible light because the visible light reflected by the object to be detected hardly reaches a light receiving surface of the light receiving element. Consequently, it is difficult to detect accurately the position of the object to be detected, in some cases.
In order to improve such a problem, a technique using an invisible light, such as an infrared light, other than the visible light is proposed. This technique, for example, is described in Japanese Patent Laid-Open Nos. 2004-318819 and 2005-275644.
With this technique, the light receiving element receives the invisible lights such as the infrared light emitted from the object to be detected to acquire the data on the received light, thereby identifying the position of the object to be detected based on the data on the received light thus acquired. In particular, it is preferable to use the infrared light because the finger of the human being has a high surface reflectivity in a wavelength of the infrared light.